Biological enhancement of estuarine benthic community structure

Abstract

Benthos in south Texas estuaries are normally concentrated in the top 3 to 4 cm where the sediment is well-oxygenated and less compact. Where larger infauna such as enteropneusts, ophiuroids, or echlurans occur in the sediments bioturbation by these infauna oxygenates and redistributes normally uninhabitated deeper sediments. A natural disturbance to Corpus Christi Bay benthos by these larger infauna could increase density and expansion of infaunal populations Into deeper reglons of the sedinlents, as well as enhance colonization by new infaunal species. During a 3.5 yr study of infaunal benthos there was a change in community structure associated with coloniza-tion of the soft-bottom habitat by the enteropneust Schizocardium n. sp. that resulted in a species composition atyplcal for a middle estuary habitat. After 2 yr the enteropneust population disappeared and the diverse and productive soft-bottom community regressed to pre-enteropneust characteristics. Increased aerobic sediments during enteropneust presence may have diminished predicted competition and encouraged development of a more diverse community than would have otherwise existed.